Check the manometer before you call anyone
Every active radon system has a U-tube manometer on the pipe, the little glass gauge with colored liquid in it. If the fluid's level on both sides, the fan's not pulling suction. PA DEP specifically tells homeowners to watch for that. It's the fastest way to know something's wrong without opening anything up, and it's the first thing I check when I get to a house too.
Why fans fail
Radon fans run around the clock, every day, for years. Most of them give out somewhere between year seven and year ten. Bearings wear down before the motor quits outright, which is why a fan usually gets noisy before it dies rather than just stopping cold. If yours has gone from a quiet hum to something you can hear inside the house, that's the bearings telling you they're on the way out, not a sign anything's about to be dangerous. It's a maintenance item, not an emergency.
A loud fan isn't always a dying fan
Vibration can come from a few places. Sometimes it's the fan itself. Sometimes it's a coupling that's worked loose, or pipe that's not properly isolated from the framing and is transmitting noise through the house structure. I check the whole run, not just the fan housing, because swapping a fan on a vibration problem that's actually coming from the pipe mounting doesn't fix anything.
A running fan doesn't prove the number's good
This is the one that trips people up. The fan's running, the manometer looks fine, and the retest still comes back above 4 pCi/L. A working fan tells you the system is active. It doesn't tell you the system was ever sized or placed right for your foundation. If that's what's going on, the fix isn't another fan, it's a look at the suction point and whether it's actually communicating with enough of the slab. I'll tell you which one you've got before I touch anything.
What actually happens on a repair or replacement
I start with the manometer and a walk of the full pipe run, inside and outside. If it's a straight fan swap, I disconnect power, remove the old fan, and match the new one to what your system actually needs, which is airflow and static pressure matched to your pipe size and suction setup, not just the highest CFM number on the shelf. Bigger isn't automatically better, and an oversized fan on an undersized system just makes noise. I reconnect with proper flexible couplings so vibration doesn't transmit into the pipe, confirm suction on the manometer, and retest. If it's not a simple swap, I'll tell you what I'm seeing and why before any parts get ordered.
Fans and foundations I run into around York County
Downtown, in Royal Square and up around Farquhar Park and the Avenues, I'm mostly dealing with rowhomes and larger Victorians on stone or rubble foundations. A fair number of those have a passive pipe that was roughed in at some point and never got a fan, which shows up looking like a repair call but is really a first activation. Out in Springettsbury, Spring Garden and the newer construction toward West York and Mount Zion Road, the foundations are almost all poured slab, and it's usually a straightforward fan swap on a system that was sized right to begin with. North York and West York have a good mix of hollow block homes from the mid-century boom, where I'm checking whether the block wall itself is affecting how the system pulls. Further out toward Shiloh, Leader Heights, Emigsville and the Susquehanna Trail corridor, I see more farmhouses with additions or a walkout basement paired with a dirt crawl space, and that's where I'm most likely to find a fan that was undersized for the actual footprint it's covering, because the original install never accounted for the second foundation zone.
What I won't do
I won't sell you a bigger fan because it sounds like a safer bet. If your existing fan and system are sized right and just old, you get a matching replacement. If the noise is a coupling, you get a coupling fix, not a new fan you didn't need. I'll tell you why, not just sell you a new one.